1. Field of the Invention
The present invention relates to a four-wheel vehicle for traveling on an irregular road, such as a saddle type four-wheel buggy.
2. Description of Background Art
As proposed in Japanese Utility Model Laid-open No. Sho 63-104117 or Publication No. Hei 5-6181 or Hei 7-23285, a vehicle for traveling on an irregular road such as a muddy, damp, sandy, snowy, or gravel road, a four-wheel vehicle may be equipped with balloon tires of a low pressure.
In such a four-wheel vehicle for traveling on an irregular road, a driving force from an engine is inputted to a multi-stage transmission through a clutch, a drive shaft is rotated with the driving force provided from the multi-stage transmission, the rotation of the driving shaft is transmitted through a propeller shaft and a differential gear to right and left driving shafts disposed transversely, and right and left front wheels (rear wheels) are rotated with rotation of the right and left driving shafts.
The differential gear generally comprises a ring gear, a pair of right and left side gears, and a pair of pinions located between the side gears and meshing with the side gears. The rotation of the propeller shaft is transmitted to the ring gear, one side gear is rotated by rotation of the ring gear, and the rotation of the one side gear is transmitted to the other side gear through a pinion. First ends of driving shafts are connected respectively through constant velocity joints to shaft portions extending outwards of the right and left side gears and the opposite ends (outer ends) of the driving shafts are connected respectively to wheels also through constant velocity joints.
As described above in connection with the conventional structure, driving shafts for the transmission of a driving force are disposed between the differential gear and the right and left front wheels, and if the driving shafts are independent suspension type driving shafts, they are connected to the differential gear through constant velocity joints so as to be swingable around their connections to the differential gear.
In order that the vehicle can travel stably, it is not desirable for the right and left wheels to have different vertical swing ranges. In this connection, making the right and left driving shafts equal in length is a precondition for ensuring a high traveling stability.
If the right and left driving shafts are made equal in length, the center of the differential gear comes to be positioned approximately on the center line of the vehicle body. Of course, if the shaft portion of one of the paired side gears which constitute the differential gear is made longer, the differential gear can be biased to either the right or the left while keeping both driving shafts equal in length. However, from the standpoint of weight balance, it is desirable that the center of the differential gear and that of the vehicle body are substantially coincident with each other.
If the differential gear is disposed substantially in alignment with the center of the vehicle body, the ring gear as a constituent of the differential gear is displaced to either the right or the left, and the propeller shaft having a gear on one end thereof which gear is in mesh with the ring gear and the drive shaft which transmits a driving force to the propeller shaft are also displaced to either the right or the left, resulting in promotion of an unbalanced state.
For remedying this unbalance in the conventional four-wheel vehicle not provided with a torque converter, the differential gear is disposed in a biased state to either the right or the left, as noted earlier, and a propeller shaft and a drive shaft are disposed on the opposite side. In this case, however, the structure of the differential gear becomes complicated; for example, the shaft portions of the right and left side gears are made different in length.
For solving the above-mentioned problems, according to the present invention there is provided a four-wheel vehicle for traveling on an irregular road wherein a driving force of an engine is transmitted to front or rear wheels, characterized in that a torque converter is provided in a power transfer path extending from a crank shaft of the engine up to an input shaft of a transmission, and a center line of a rotational axis of the torque converter and a longitudinal center line of a drive shaft which transmits the driving force from the transmission to the front or rear wheel are positioned right and left in an opposed relation to each other with respect to a longitudinal center line of a body of the vehicle.
According to the above construction, the torque converter and the drive shaft, which are heavy components, are distributed right and left. Consequently, the vehicle is weight-balanced and its traveling stability is enhanced.
Further, if the differential gear, which is also a heavy component, is disposed centrally of the vehicle body, the vehicle is more weight-balanced.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.